Gas insulation apparatus

ABSTRACT

A gas insulation apparatus has a sealed container, an insulation gas, a high-voltage portion, and a removal material. The insulation gas has CO2 and O2 filling the sealed container as main components. The high-voltage portion is stored in the sealed container. The removal material reduces concentrations of HF, CO, and O3 in the insulation gas.

TECHNICAL FIELD

An embodiment of the present invention relates to a gas insulationapparatus.

BACKGROUND ART

In a gas insulation apparatus performing power transmission anddistribution in an electric power system, in the related art, sulfurhexafluoride (which will hereinafter be described as SF₆) is used aninsulation gas.

Since SF₆ has a global warming potential (GWP) of 23,500 (AR5; thelatest value according to the IPCC fifth assessment report) andsignificantly affects the environment at the time of leakage,alternative gas insulation apparatuses using carbon dioxide (which willhereinafter be described as CO₂), which has a lower environmentalburden, as an insulation gas are attracting attention. When CO₂ is usedas an insulation gas, it is known that an effect of improving a breakingperformance and a dielectric strength can be achieved by mixing oxygen(which will hereinafter be described as O₂) therewith.

When an insulation gas sealed inside a gas insulation apparatus isexposed to an arc during opening/closing operation, decompositionproducts are generated. These decomposition products include undesiredsubstances which adversely affect the performance of equipment, and thusthere is a need to provide countermeasures for removing them from theinsulation gas, such as adsorption using an adsorbent or the like. Inaddition, during maintenance, there is also a need to secure safety ofdecomposition products with respect to the human body. Regardingdecomposition products, for example, a value of LC 50 or the like is setfor each of CO, HF, and O₃, and they become noxious with respect to thehuman body at a concentration of a certain value or larger. Therefore,there is a need to reduce these.

A usage environment of an adsorbent when the adsorbent is installed in agas insulation apparatus is mainly in a standstill state at a normaltemperature, so that an insulation gas comes into contact with theadsorbent due to a convection flow, thereby resulting in adsorption. Forthis reason, active inflow of a target gas cannot be expected. Such anadsorbent is required to sufficiently adsorb decomposition products asnecessary in a special usage environment as well.

Undesired substances such as SOF₂, HF, and SO₂ have become particularlyproblematic among decomposition products in insulation equipment using aSF₆ gas in the related art. SOF₂ is derived from SF₆ and a very smallamount of H₂O included in the gas. HF is derived from SOF₂, PTFE ofequipment constituent components, and a very small amount of H₂Oincluded in the gas. SO₂ is derived from SOF₂ and a very small amount ofH₂O included in the gas.

The foregoing undesired substances have a smaller molecular size thanSF₆ (insulation gas). Therefore, by selecting an adsorbent such that arelationship of SF6>pore size of adsorbent>undesired substances isestablished, the undesired substances can be preferentially adsorbed byphysical adsorption utilizing molecular sieve action.

On the other hand, the main undesired substances in a gas insulationapparatus using a CO₂ gas are HF, CO, and O₃. HF is derived from a verysmall amount of H₂O included in the gas and PTFE of equipmentconstituent components. Particularly, when O₂ is mixed with CO₂ as aninsulation gas, generation of CO is curbed to an extent that it can beadsorbed. On the other hand, generation of O₃ tends to increase. Themolecular size of molecules of CO₂ is approximately 0.33 nm, which issmaller than 0.550 nm of SF₆, and is a molecular size which isapproximately the same as those of undesired substances (HF, CO, andO₃). Therefore, in physical adsorption utilizing molecular sieve actionby means of the pore size of an adsorbent, CO₂ (insulation gas) isadsorbed, and thus the foregoing undesired substances cannot besufficiently adsorbed.

HF is bonded to a very small amount of H₂O included in the gas, reactswith metal materials (Fe, Al), causes corrosion, and is poisonous to thehuman body when it is released to the atmosphere. In addition, CO ispoisonous to the human body when it is released to the atmosphere. Inaddition, if a large amount of CO is generated (vol % order), there isconcern that the dielectric strength may be degraded. Moreover, there isconcern that O₃ may extremely impair a life span of a lubricant and aseal material (resin) due to ozone cracking, and it is poisonous to thehuman body when it is released to the atmosphere.

CITATION LIST Patent Literature [Patent Literature 1]

-   Japanese Patent No. 4660407

[Patent Literature 2]

-   Japanese Patent No. 5238622

SUMMARY OF INVENTION Technical Problem

In order to resolve the problems, the present invention provides a gasinsulation apparatus in which concentrations of HF, CO, and O₃ in aninsulation gas are reduced.

Solution to Problem

A gas insulation apparatus according to an embodiment has a sealedcontainer, an insulation gas, a high-voltage portion, and a removalmaterial.

The insulation gas has CO₂ and O₂ filling the sealed container as maincomponents.

The high-voltage portion is stored in the sealed container.

The removal material reduces concentrations of HF, CO, and O₃ in theinsulation gas.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view illustrating a cross section of a gasinsulation breaker according to a first embodiment.

FIG. 2 is a graph showing a removal performance with respect to HF, CO,and O₃ of a removal material 1.

FIG. 3 is a graph showing a removal performance with respect to HF, CO,and O₃ of a removal material 2.

FIG. 4 is a graph showing a removal performance with respect to HF, CO,and O₃ of a removal material 3.

FIG. 5 is a graph showing a removal performance with respect to HF, CO,and O₃ of a removal material 4.

DESCRIPTION OF EMBODIMENT

Hereinafter, a gas insulation apparatus according to an embodiment willbe described with reference to the drawings.

In order to resolve the foregoing problems, various research and testshave been performed. Consequently, it has been confirmed that aconcentration of HF, CO, or O₃ in an insulation gas can be sufficientlyreduced and a life span and reliability of a gas insulation apparatususing an insulation gas having CO₂ and O₂ as main components can besecured in long-term use by using a removal material constituted of anadsorbent or a catalyst manifesting selective adsorption actiondepending on a polarity and catalytic action. The present invention isbased on this knowledge.

First Embodiment

A first embodiment will be described using FIG. 1. A gas insulationapparatus according to the present embodiment is a puffer-type gasinsulation breaker. FIG. 1 is a partial schematic cross-sectional viewof the gas insulation apparatus (gas insulation breaker) according tothe present embodiment.

As illustrated in FIG. 1, an insulation gas 2 fills the inside of asealed container 1 constituted of a ground metal, a porcelain tube, orthe like. Inside the sealed container 1, a fixed contact portion 31 anda movable contact portion 41 are disposed so as to face each other, anda fixed arc contactor 32 and a movable arc contactor 42 are respectivelyprovided in the fixed contact portion 31 and the movable contact portion41. A high-voltage portion is constituted of the fixed contact portion31 and the movable contact portion 41. An O-ring or the like is disposedat a sealing location of the sealed container 1, thereby forming anairtight structure.

The arc contactors 32 and 42 are in a contact conduction state duringnormal operation, and they separate from each other and generate an arc7 in a space between both the contactors 32 and 42 due to relativemovement during breaking operation. Moreover, a gas flow generationmeans for spraying the insulation gas 2 (arc-extinguishing gas) to thearc 7 is installed on the movable contact portion 41 side.

Here, as the gas flow generation means, a piston 43, a cylinder 44, andan insulation nozzle 45 are provided. In addition, a metal exhaustcylinder 33 through which a hot gas flow 8 can pass is attached to thefixed contact portion 31 side. An exhaust rod 46 through which the hotgas flow 8 can pass is provided on the movable contact portion 41 sideso as to lead to the movable arc contactor 42. A grease for reducingfriction is applied to sliding portions of the piston 43 and thecylinder 44.

Regarding an insulation gas which fills the inside of the sealedcontainer 1 and also functions as an arc-extinguishing gas, a gas havingCO₂ and O₂ as main components is used. 50% or more by volume % of CO₂ isincluded, and O₂ is included within a range not exceeding 50% by volume%. Specifically, a mixed gas of CO₂ (70%) and O₂ (30%) can be presentedas an example.

In addition, even when a gas having a larger molecular size than CO₂ ismixed into the insulation gas for the purpose of improving a dielectricstrength, the effects of the present embodiment can be achieved.Examples of the mixed gas include compounds containing fluorine andiodine, such as hydrofluoromonoether, perfluoroketone,hydrofluoroolefin, perfluoronitrile, or trifluoroiodomethane.

Inside the sealed container 1, a removal material 6 having a function ofreducing the concentrations of HF, CO, and O₃ in the insulation gas isinstalled. The removal material 6 is held inside the sealed container 1by a case 5. An effect of more actively reducing the concentrations ofHF, CO, and O₃ can be achieved by disposing the removal material 6 on aflow channel of the arc-extinguishing gas on an exit side of the exhaustcylinder 33.

The removal material 6 reduces the concentrations of HF, CO, and O₃ inthe insulation gas by adsorbing, oxidizing, or reducing thesesubstances. For example, regarding the removal material 6, a syntheticzeolite in which a mole ratio of silica/alumina is 5 or higher (whichmay hereinafter be referred to as a high silica synthetic zeolite), asynthetic zeolite having protons (H) as positive ions (which mayhereinafter be referred to as a proton exchange synthetic zeolite), anda metal oxide can be presented as examples. In addition, the removalmaterial 6 may be a combination of two or more kinds of a high silicasynthetic zeolite, a proton exchange synthetic zeolite, and a metaloxide.

Moreover, the removal material 6 may be a combination of materials otherthan a high silica synthetic zeolite, a proton exchange syntheticzeolite, and a metal oxide. For example, a mixture of a material havinga removal performance with respect to HF, a material having a removalperformance with respect to CO, and a material having a removalperformance with respect to O₃ may be used as the removal material 6according to the present embodiment.

Regarding a high silica synthetic zeolite, for example, a high silicazeolite having a pore size of 4.9 Å and having protons as positive ionscan be presented as an example. In addition, regarding a proton exchangesynthetic zeolite, for example, a zeolite having a pore size of 4.9 Åcan be presented as an example. Moreover, regarding a metal oxide, CuO,CO₃O₄, and MnO₂ can be presented as examples.

Regarding a zeolite, generally, it is known that the strength andreaction activity as a solid acid increase as the mole ratio of alumina(Al₂O₃) to silica (SiO₂) becomes high. When a high silica zeolite havinga silica/alumina ratio is 5 or higher is used as the removal material 6,the removal material 6 manifests catalytic action of oxidizing CO intoCO₂ as a solid acid. In addition, the speed of O₃ changing to O₂ due toself-reaction is accelerated. HF is physically adsorbed into the poresdue to an intermolecular force (Van der Waals force) generated dependingon the polarity of the zeolite. Accordingly, due to the high silicasynthetic zeolite, three kinds of undesired substances, such as HF, CO,and O₃, can be effectively adsorbed, oxidized, and reduced.

In addition, when protons (H⁺) are adopted as positive ions of thesynthetic zeolite, it can be used as a solid acid and manifestscatalytic action of oxidizing CO into CO₂. In addition, the speed of O₃changing to O₂ due to self-reaction is accelerated. HF is physicallyadsorbed into the pores due to an intermolecular force (Van der Waalsforce) generated depending on the polarity of the zeolite. Accordingly,due to the proton exchange synthetic zeolite, three kinds of undesiredsubstances, such as HF, CO, and O₃, can be effectively adsorbed,oxidized, and reduced.

Moreover, metal oxides such as CuO, CO₃O₄, and MnO₂ have a function of acatalyst at least within a temperature range of −30° C. to 50° C. Sincethese metal oxides are oxidation catalysts, they manifest catalyticaction of oxidizing CO into CO₂. In addition, the speed of O₃ changingto O₂ due to self-reaction is accelerated. HF is physically adsorbed ona surface of the catalyst due to an intermolecular force (Van der Waalsforce) generated depending on the polarity. Accordingly, due to themetal oxide, three kinds of undesired substances, such as HF, CO, andO₃, can be effectively adsorbed, oxidized, and reduced.

A metal oxide may be added to a coating material such that an innersurface of the sealed container 1 is coated therewith, and thus theinner surface of the sealed container 1 can have a function of acatalyst.

In a breaking process of the gas insulation breaker having the foregoingconstitution, when the movable contact portion 41 operates in theleftward direction in FIG. 1, the fixed piston 43 compresses a pufferchamber 47 that is an internal space of the cylinder 44 and raises thepressure therein. Further, the insulation gas 2 present inside thepuffer chamber 47 becomes a high-pressure gas flow, is guided to theinsulation nozzle 45, and is strongly sprayed to the arc 7 generatedbetween the arc contactors 32 and 42. Accordingly, the conductive arc 7generated between the arc contactors 32 and 42 disappears and a currentis blocked.

When O₂ is mixed into a gas including CO₂ and an arc is ignited, thereis a likelihood that HF, CO, and O₃ are generated. HF is a gas havingcorrosiveness particularly with respect to a metal and is noxious withrespect to the human body. CO is a toxic gas and degrades the dielectricstrength of the insulation gas. O₃ is also a gas having high reactivityand being poisonous to the human body. In addition, O₃ causes the O-ringused for the sealed container 1 retaining the airtight structure orgrease applied to the sliding portions of the piston 43 and the cylinder44 to deteriorate. When the removal material 6 having a function ofreducing the concentrations of HF, CO, and O₃ in the insulation gas isinstalled inside the sealed container 1, these poisonous gases can beadsorbed, oxidized, or reduced, safety can be enhanced, and the lifespan of the equipment can be lengthened.

Table 1 shows performances of various kinds of removal materials. Aremoval material 1 is a proton exchange synthetic zeolite in which themole ratio of silica/alumina is 5 and the pore size is 4.9 Å. A removalmaterial 2 is a potassium exchange synthetic zeolite in which the moleratio of silica/alumina is smaller than 5 and the pore size is 3 Å. Aremoval material 3 is a sodium exchange synthetic zeolite in which themole ratio of silica/alumina is smaller than 5 and the pore size is 9 Å.A removal material 4 is a lithium exchange synthetic zeolite in whichthe mole ratio of silica/alumina is smaller than 5 and the pore size is9 Å. The marks “G” in Table 1 indicate that a sufficient performance canbe exhibited when being used in the gas insulation breaker illustratedin FIG. 1, and the marks “B” indicate that a sufficient performancecannot be exhibited. In addition, in FIGS. 2 to 5, removal performancesof the removal materials 1 to 4 are shown in graphs. In FIGS. 2 to 5,the horizontal axis indicates the time, and the vertical axis indicatesthe concentrations of HF, CO, and O₃ illustrated in FIG. 1, that is, thegenerated concentration (volume ppm) per 1 MJ of a breaking currentenergy in the gas insulation breaker. As shown in Table 1 and FIGS. 2 to5, it is ascertained that the removal material 1 can exhibit asufficient effect of reducing the concentration with respect to all ofHF, CO, and O₃.

TABLE 1 HF CO O₃ Removal material 1 G G G Removal material 2 B B BRemoval material 3 G B G Removal material 4 G B G

The gas insulation apparatus of the present embodiment includes a gasinsulation opening/closing apparatus. A gas insulation opening/closingapparatus includes a breaker, a disconnector, a grounding switch, and alightning arrestor.

According to at least one embodiment described above, when a removalmaterial is used, a gas insulation apparatus reducing the concentrationsof HF, CO, and O₃ in the insulation gas can be provided. Accordingly, alife span and reliability of a gas insulation apparatus using aninsulation gas having CO₂ and O₂ as main components can be secured inlong-term use, and safety during maintenance can also be secured.

Some embodiments of the present invention have been described, but theseembodiments are presented as examples and are not intended to limit thescope of the invention. These embodiments can be performed in variousother forms, and various omissions, replacements, and changes can beperformed within a range not departing from the gist of the invention.These embodiments and modifications thereof are included in theinvention described in the claims and the scope equivalent thereto asthey are included in the scope and the gist of the invention.

REFERENCE SIGNS LIST

-   -   1 Sealed container    -   2 Insulation gas    -   6 Removal material    -   31 Fixed contact portion (high-voltage portion)    -   41 Movable contact portion (high-voltage portion)

1. A gas insulation apparatus comprising: a sealed container; aninsulation gas that has CO₂ and O₂ filling the sealed container as maincomponents; a high-voltage portion that is stored in the sealedcontainer; and a removal material that reduces concentrations of HF, CO,and O₃ in the insulation gas.
 2. The gas insulation apparatus accordingto claim 1, wherein the removal material is a synthetic zeolite in whicha mole ratio of silica/alumina is 5 or higher.
 3. The gas insulationapparatus according to claim 1, wherein the removal material is asynthetic zeolite having protons (H) as positive ions.
 4. The gasinsulation apparatus according to claim 1, wherein the removal materialis a metal oxide.
 5. The gas insulation apparatus according to claim 1,wherein the removal material is constituted of a combination of two ormore kinds of materials.
 6. The gas insulation apparatus according toclaim 1, wherein the insulation gas includes a gas component having alarger molecular size than CO₂.
 7. The gas insulation apparatusaccording to claim 1, wherein the gas insulation apparatus is anopening/closing apparatus, and wherein the high-voltage portion includesa fixed contactor, a movable contactor which is able to come intocontact with or separate from the fixed contactor, is disposed so as tocoaxially face the fixed contactor, and is constituted such that arcdischarge is able to be generated between the movable contactor and thefixed contactor at a time of separation, and an insulation nozzle whichis disposed such that the arc discharge is surrounded in order to spraythe insulation gas to the arc discharge.
 8. The gas insulation apparatusaccording to claim 7, wherein the insulation nozzle includes afluorine-based resin.
 9. The gas insulation apparatus according to claim7, wherein the removal material is disposed at a position where theinsulation gas is able to flow after being sprayed to the arc discharge.